Mechanical compatibility of sol–gel annealing with titanium for orthopaedic prostheses

Sol–gel processing is an attractive method for large-scale surface coating due to its facile and inexpensive preparation, even with the inclusion of precision nanotopographies. These are desirable traits for metal orthopaedic prostheses where ceramic coatings are known to be osteoinductive and the effects may be amplified through nanotexturing. However there are a few concerns associated with the application of sol–gel technology to orthopaedics. Primarily, the annealing stage required to transform the sol–gel into a ceramic may compromise the physical integrity of the underlying metal. Secondly, loose particles on medical implants can be carcinogenic and cause inflammation so the coating needs to be strongly bonded to the implant. These concerns are addressed in this paper. Titanium, the dominant material for orthopaedics at present, is examined before and after sol–gel processing for changes in hardness and flexural modulus. Wear resistance, bending and pull tests are also performed to evaluate the ceramic coating. The findings suggest that sol–gel coatings will be compatible with titanium implants for an optimum temperature of 500 °C

Increased efficiency of direct nanoimprinting on planar and curved bulk titanium through surface modification

In this work the direct transfer of nanopatterns into titanium is demonstrated. The nanofeatures are imprinted at room temperature using diamond stamps in a single step. We also show that the imprint properties of the titanium surface can be altered by anodisation yielding a significant reduction in the required imprint force for pattern transfer. The anodisation process is also utilised for curved titanium surfaces where a reduced imprint force is preferable to avoid sample deformation and damage. We finally demonstrate that our process can be applied directly to titanium rods

An empirical analysis of financial stress within South Africa and its apparent co-movement with financial stress emanating from advanced and emerging economies

The identification of financial stress, and an understanding of financial contagion on a global scale, is of critical importance to a South African economy that is becoming increasingly integrated into the global economy. The last decade has been characterised by periods of high economic growth, but also periods of significant financial instability culminating in global economic crises. This study examines the extent to which the South African financial system is exposed to distress abroad by identifying and measuring the co-movement of financial stress originating from within and outside South Africa. The study can be separated into two sections: the identification of financial stress and the measurement of financial contagion. Using monthly data for the period 2000 to 2012, three indices were constructed for the emerging markets, advanced economies and South Africa using varianceequal weighting. The indices were tested for contagion using the Johansen and Jesulius (1990) multivariate cointegration approach supplemented with basic OLS architecture and Impulse Response analysis. The results indicate the three constructed indices were highly accurate at identifying the intensity and timing of financial stress over the three regions respectively. It was found that the South African financial sector is highly susceptible to financial stress originating from advanced economies. The results obtained for financial stress emanating from emerging markets were not as conclusive and found to be insignificant. Overall, it is clear that the methods employed to identify financial stress are highly accurate and that South Africa is highly susceptible to financial stress originating from abroad. It is clear that advanced economies have a greater ability to affect financial stress in South Africa via contagion. It must be noted that this does not conclude that South Africa is not affected by emerging market crises, but that these crises tend to affect South Africa through advanced economy channels as defined within this thesis

Nanopatterning titanium and PEEK for orthopaedic implants

This project was inspired by research by Dalby and Gadegaard that demonstrated nanopatterning of poly-methyl-methacrylate (PMMA) surfaces can stimulate mesenchymal stromal cells (MSCs) to differentiate into osteoblasts and produce bone mineral in vitro.[1] The motivation for this thesis was to adapt and upscale the technology for clinical application, with the aim of fabricating osteogenic imlants for orthopaedic surgery, such as intervertebral fusion cages.[2] This translation would initially involve injection mould nanopatterning poly-ether-ether-ketone (PEEK) surfaces. A further objective was to discover methods for fabricating non-planar moulds that could be used in the injection mould nanopatterning process. Nanoimprint lithography of a novel titanium dioxide precursor sol-gel was performed using flexible polydimethylsiloxane (PDMS) stamps that could conform to non-planar contours of injection mould inlays as a demonstration of the technology. Subsequent injection moulding showed initial success, but the titanium dioxide nanopillars lacked the durability required for repeated moulding cycles. Nanopatterned PEEK surfaces produced by injection moulding (using electroplated nickel inlays) were assessed to determine whether the nanopatterns exhibited any biological effect upon human bone marrow cells. Initial in vitro experiments by Dr Daniel Morrison and a collaborative group in Davos raised concerns regarding cell adhesion on nanopatterned PEEK surfaces and additional work was undertaken to modify PEEK using oxygen plasma treatment.[3] The use of a cell seeding device designed by Dr Paul Reynolds, led to more reliable in vitro results as it provided a more favourable environment for cell adhesion. Due to the opacity and autofluorescence of PEEK, in vitro analysis used histological staining with reflected light microscopy and quantitative reverse transcriptase PCR. In vitro experimentation revealed that oxygen plasma treatment increased cell adhesion but reduced the bioactive effect of nanopatterning. Although bone marrow cells adhered to the PEEK nanopatterns in small numbers, the cells exhibited a more osteogenic phenotype, demonstrated by relative increased in calcium and phosphate expression. Nanopatterned PEEK did not achieve the results required for progression to an in vivo study. Therefore, surface coating nanopatterned PEEK was considered as an alternative method to satisfy the objectives of the project. An in vivo study was undertaken in collaboration with Nijmegen to study osseointegration of titanium coated injection mould nanopatterned surfaces. Due to intellectual property negotiations, polycarbonate was used rather than PEEK and the NSQ and HEX nanopatterns were not included. The titanium coated nanopatterned implants demonstrated significantly increased bone to implant contact compared to commercially developed grit-blasted acid-etched titanium implants. With a view to further pre-clinical studies of nanopatterned implants, improved in vivo models of osseointegration and osteogenesis in rabbits were developed. These will enable the assessment of novel implants and satisfied the UK Home Office requirements for reduction, refinement and replacement of animal models. Although not suitable for use in high performance injection mould inlays, the titanium dioxide precursor sol-gel developed for this thesis could be used to directly nanopattern orthopaedic implant surfaces, thus promoting osteogenesis. Furthermore, as demonstrated by the in vivo study presented in this thesis, injection mould nanopatterned polymeric implants (such as PEEK) can be modified with an ultra-thin layer of titanium to improve osseointegration. The work described herein has highlighted that nanopatterning will not necessarily provide the same results in different materials. It does, however, provide further evidence to support the hypothesis that nanopatterning directs cell behaviour by nanotopographical changes in surface chemistry and surface energy which affect cell adhesion

Runt-Related Transcription Factor 2 Induction During Differentiation of Wharton's Jelly Mesenchymal Stem Cells to Osteoblasts Is Regulated by Jumonji AT-Rich Interactive Domain 1B Histone Demethylase

Indexación: ScopusNovel bone regeneration approaches aim to obtain immature osteoblasts from somatic stem cells. Umbilical cord Wharton's jelly mesenchymal stem cells (WJ-MSCs) are an ideal source for cell therapy. Hence, the study of mechanisms involved in WJ-MSC osteoblastic differentiation is crucial to exploit their developmental capacity. Here, we have assessed epigenetic control of the Runt-related transcription factor 2 (RUNX2) osteogenic master regulator gene in WJ-MSC. We present evidence indicating that modulation of RUNX2 expression through preventing Jumonji AT-rich interactive domain 1B (JARID1B) histone demethylase activity is relevant to enhance WJ-MSC osteoblastic potential. Hence, JARID1B loss of function in WJ-MSC results in increased RUNX2/p57 expression. Our data highlight JARID1B activity as a novel target to modulate WJ-MSC osteoblastic differentiation with potential applications in bone tissue engineering. Stem Cells 2017;35:2430–2441. © 2017 AlphaMed Presshttps://academic-oup-com.recursosbiblioteca.unab.cl/stmcls/article/36/4/631/645310

A Christian Philosophy of History: St. Augustine and The City of God

St. Augustine was an influential member of the early Christian Church, establishing many doctrines of the Christian faith. One of his most significant contributions to Christianity was a Christian philosophy of history. Augustine defined the purpose of history as God providing salvation to humanity after the fall of Adam. This salvation is achieved through a conflict between two cities of people, the earthly city and the City of God, which are defined by two separate loves. The earthly citizens love themselves more than God, while the citizens in the City of God love God more than themselves. Salvation is ultimately provided to the predestined citizens of the City of God in the final judgment, while citizens of the earthly city are damned to eternal punishment in a pit of fire. This philosophy of history broke with the classical tradition history, which believed that history was cyclic, repeating continuously for all eternity. Augustine defined history as having a distinct beginning and end, through which God worked to provide salvation to humanity

The Relationship between Self-Enhancing Humor, Self-Compassion, and Emotional Traits

This research focused on characterizing the relationship between self-enhancing humor, self-compassion, and long-term emotional traits.. It was hypothesized that self-enhancing humor would be related to self-compassion and the related subscales of mindfulness and self-kindness. In addition, it was predicted that self-enhancing humor would relate most strongly to positive emotional traits. The data supported both of these hypotheses, which allowed for the construction of a model of the psychological variables that predict self-enhancing humor, a task that has yet to be seriously undertaken. This research provides significant inspiration for further exploration of this topic

Chemostratigraphy and provenance of clays and other non-carbonate minerals in chalks of Campanian age (Upper Cretaceous) from Sussex, southern England

Geochemical analysis of acid-insoluble residues derived from white chalks and marl seams of Campanian age from Sussex, UK, has been undertaken. All display a broadly similar <2 μm mineralogical composition consisting of smectite or smectite-rich illite-smectite with subordinate illite and minor amounts of talc. Plots of K2O/Al2O3 and TiO2/Al2O3 indicate that most marl seams have an acid-insoluble residue composition which is slightly different to that of the over- and underlying white chalk, implying that marl seams are primary sedimentary features not formed through white chalk dissolution. On the basis of a negative Eu anomaly and trace element geochemistry one marl seam, the Old Nore Marl, is considered to be volcanically derived and best classified as a bentonite; it is considered to correlate with the bentonite M1 of the north German succession

3D bioactive composite scaffolds for bone tissue engineering

Bone is the second most commonly transplanted tissue worldwide, with over four million operations using bone grafts or bone substitute materials annually to treat bone defects. However, significant limitations affect current treatment options and clinical demand for bone grafts continues to rise due to conditions such as trauma, cancer, infection and arthritis. Developing bioactive three-dimensional (3D) scaffolds to support bone regeneration has therefore become a key area of focus within bone tissue engineering (BTE). A variety of materials and manufacturing methods including 3D printing have been used to create novel alternatives to traditional bone grafts. However, individual groups of materials including polymers, ceramics and hydrogels have been unable to fully replicate the properties of bone when used alone. Favourable material properties can be combined and bioactivity improved when groups of materials are used together in composite 3D scaffolds. This review will therefore consider the ideal properties of bioactive composite 3D scaffolds and examine recent use of polymers, hydrogels, metals, ceramics and bio-glasses in BTE. Scaffold fabrication methodology, mechanical performance, biocompatibility, bioactivity, and potential clinical translations will be discussed

Surface topography regulates wnt signaling through control of primary cilia structure in mesenchymal stem cells

The primary cilium regulates cellular signalling including influencing wnt sensitivity by sequestering β-catenin within the ciliary compartment. Topographic regulation of intracellular actin-myosin tension can control stem cell fate of which wnt is an important mediator. We hypothesized that topography influences mesenchymal stem cell (MSC) wnt signaling through the regulation of primary cilia structure and function. MSCs cultured on grooves expressed elongated primary cilia, through reduced actin organization. siRNA inhibition of anterograde intraflagellar transport (IFT88) reduced cilia length and increased active nuclear β-catenin. Conversely, increased primary cilia assembly in MSCs cultured on the grooves was associated with decreased levels of nuclear active β-catenin, axin-2 induction and proliferation, in response to wnt3a. This negative regulation, on grooved topography, was reversed by siRNA to IFT88. This indicates that subtle regulation of IFT and associated cilia structure, tunes the wnt response controlling stem cell differentiation.We acknowledge funding from an EPSRC Platform grant which supported McMurray and a Wellcome Trust project grant which supported Wann and McMurray. Wann is now supported on an ARUK project grant. Thompson was funded by a BBSRC PhD studentshi